Over 1.1 million Americans experience a cardiac arrest each year. Of that number about 500,000 die, or about twice the number that die from any other cause, including accidents. Approximately half of these incidents occur within the hospital.
The first 4-6 minutes from the onset of cardiac arrest to treatment are crucial in obtaining a successful outcome. Therefore early detection, or better anticipation of the event is critical in positively impacting patient outcomes. Traditional methods for early detection are too costly to be broadly deployed. Current methods include continuous monitoring within the hospital setting through either fixed intensive care monitoring or ambulatory telemetry monitoring. The capital cost of current technology is approximately $12,000 to $30,000 per device and requires high technical skill levels to use the devices and related systems effectively.
Continuous vital signs monitoring systems are well known to those skilled in the art. Hospitals have broadly adopted such systems in the early 1960s as intensive care units emerged as a standard of care. These early systems utilized proprietary network connectivity from a plurality of bedside monitors to a central viewing station. Early systems were based on both hardwired analog and digital communications methods. These systems migrated to standards based IEEE 802.3 Ethernet-based digital communications systems in the 1980s, as Ethernet technologies matured and became cost effective to implement. Hardwired systems expanded in the hospital as medical care subspecialties grew, but were generally restricted to intensive care settings.
Concurrent with the development and growth of hardwired systems, one-way telemetry systems were created that allowed ECG monitoring of patients during ambulation. Early systems emerged from NASA development in the early '60s for monitoring of astronauts. Simple analog radios operating in the unused VHF and UHF spectrum with simple modulation schemes grew in coronary care step-down units. These systems operated under Part 15 of the FCC Rules in unused portions of the television spectrum.
Telemetry technology improved with one-way digital communications in the 1980s. Additional parameters were added, first by Siemens in adding blood oxygen saturation (SPO2) and then by others in the late 1980s.
In 1992 Welch, et al., patented for the first time a system that allowed central surveillance monitoring to be decoupled from intensive care or coronary care step down environments. This patent, U.S. Pat. No. 5,319,363, allowed central surveillance to be accessible to any bedside location without dedicating devices to these beds. The '363 patent further provided for both two-way hardwired and wireless communications methods. Protocol Systems, Inc., later acquired by Welch Allyn, Inc. of Skaneateles, N.Y., commercialized this invention.
In terms of other known prior art, Dempsey, U.S. Pat. Nos. 5,579,001, 5,579,775 and 5,687,734 each describe a two-way telemetry apparatus that uses a backchannel receiver to carry control signals between a proprietary wireless network and a bedside monitor. Additionally, Dempsey further describes a system apparatus that combines traditional one-way medical telemetry and traditional one-way (opposite) paging systems to achieve bi-directional communications. Flach, et al., U.S. Pat. Nos. 5,767,791 and 5,748,103, describe a combined bidirectional telemetry system that optimizes available bandwidth with modulation schemes such as frequency hopping. VitalCom, later acquired by GE Medical Systems, has since commercialized the subject matter described by this latter patent.
West, et al., U.S. Pat. Nos. 6,544,173 and 6,544,174, improved upon the Welch '363 patent describing a two-way standards based wireless patient monitor and system that provides connectivity to a plurality of central stations in an enterprise wide real-time monitoring network. The West patents also describe a patient wearable device that can be configured in either a connected state or a non-connected state.
Besson et al., U.S. Pat. No. 5,682,803, describes a wireless two-way sensor with error correcting means that can be used to control and manipulate the data communicating between a patch electrode and a bedside monitor. Besson's intent was to eliminate the wires between sensors and bedside monitors.
DeLuca, U.S. Pat. No. 6,440,067B1, describes a system that includes body worn sensors communicating to a body worn repeater which in turn communicates to a base station for transmission over a telephone line or internet to a central review station. DeLuca's device is designed for the monitoring of physical activity that is associated with a specific “non-communicating” activity.
All of the above known references, and others as referenced that are referenced by these patents, commonly describe a real time, continuous physiologic monitoring system. The devices described by each of these patents are intended to be in a continuous connected state when configured with an associated system. The consequence of this requirement is a network that requires sufficient power to support a continuously connected instrument. Therefore, for wireless connectivity, sufficiently sized batteries must be incorporated in order to achieve acceptable useful life for the combined apparatus.
The above noted '803 Besson patent and its progeny is especially aware of this requirement and teaches means for powering wireless sensors to support the sensor and the wireless link. Besson et al. further provides error correcting means, as well as control and manipulation of the communications data, in order to achieve high data throughput quality at minimum RF power levels. DeLuca also recognizes this limitation and provides for recharging means for his described body-worn sensors.
Therefore, there is a general need in the field for a low cost, simple to use diagnostic monitoring device. The potential market for such a device goes well beyond the more than 61 million Americans who are classified as having some form of cardiovascular disease. The US military is also actively investigating personal status monitoring for its deployed military personnel. Military sources estimate an annual volume of 40,000 units. It is a therefore primary object of the present invention to address the above-noted need in the diagnostic field.